Swainson's Warbler
Limnothlypis swainsonii
Shy and difficult to see in deciduous forest with dense understory, often near water. Plain buffy-brown coloration with rufous crown and dark eyeline. Also note disproportionately large, sharp, pinkish bill and pink legs. Shimmies tail side-to-side as it slowly forages on the forest floor, investigating fallen leaf litter for insects. Fairly restricted breeding range in the southeastern U.S.; winters primarily on the Yucatan peninsula and in the Caribbean. Listen for loud, sweet song, similar to Louisiana Waterthrush but without the complex ending.
识别特征
Swainson's warblers are a small and rather nondescript songbird, though are fairly large for a New World warbler. Adults grow to 12.5–16 cm (4.9–6.3 in) in length and 11–20.5 g (0.39–0.72 oz) in weight. The wingspan averages 23 cm (9.1 in). They are a plain olive-brown above and pale yellow-white below. They have a whitish eyebrow stripe that runs above their eye, and the top of their head is a rusty brown. Unlike most other New World warblers that are mostly dimorphic, there is no difference in appearance between a male or female Swainson's warbler.
分类信息
No subspecies are recognized. There appears to be some divergence between populations from Arkansas and others of the coastal plains. This does fit a pattern one would expect from genetic drift, but there seem to be no geographical or ecological barriers restricting gene flow. Even during the last ice age, when average temperatures, precipitation and sea levels were lower, there seems to have been ample contiguous habitat. Clearly, some factor restricting gene flow is at work, but it is not presently known what it is. It is possible that the subpopulations conform to the different wintering areas.<p>In some migrant birds it is known that the initial direction of the migration is set by fairly simple hereditary mechanisms. Offspring of pairs comprising birds of different subpopulations will, in such species, attempt to migrate into an intermediate direction. Such a course would lead a Swainson's warbler deep into the Caribbean where there are no wintering or even stopover points, and the bird would almost certainly perish. More research such as analyzing bird banding data is needed to determine whether this mechanism applies in Swainson's warbler.
- 学名
- Limnothlypis swainsonii
- 命名信息
- (Audubon, 1834)
- 目
- Passeriformes
- 科
- Parulidae
- 属
- Limnothlypis
分布与栖息地
Swainson's warblers are uncommon, mostly found in flooded swamplands and canebrakes of the south-eastern United States. More rarely, they will also occur in rhododendron thickets in the southern Appalachian Mountains. They are a migratory species, with part of the population migrating southeastwards to the Greater Antilles (where it overwinters in the Blue Mountains of Jamaica for example) and the other southwestwards to the Yucatán Peninsula region in winter.
- 繁殖区
- NA : se USA
- 非繁殖区
- MA and West Indies
- 迁徙
- Complete migrants
行为
This species begins breeding at about 10 months of age. Pairs form, and stake out and defend a territory for nesting. Nests are fairly large and bulky, constructed from moss, grass, and small leaves situated above ground in a tangle of tall reeds or vines. The female will lay between three and five eggs. The eggs are white and sometimes, but rarely, speckled with brown. Incubation is done by the female only and lasts for about 14 days, after which the eggs will hatch. The young leave the nest about 12 days later. It is not known how long pairs stay together, although once a pair-bond has been established they do not usually mate with other birds at least in the current nesting season. These birds live to as old as eight years.
保护状况
- 种群趋势
- rising
照片
分布
鸟叫声
其他鸟类
Lesser Crested Tern
Thalasseus bengalensis
Elegant medium-sized tern with a slender yellow-orange bill and black crown. Can be confused with Great Crested Tern; note proportionally longer, more orangey bill on Lesser Crested. Also note gray upperwing, which separates it from Sandwich Tern. Gray rump and tail are diagnostic if seen well. On juveniles, note dull legs, secondaries with dark centers, and a weakly patterned upperwing. Strictly coastal, usually found on beaches and estuaries. Call a noisy “kerrrick.”
Cinnamon Attila
Attila cinnamomeus
Medium-sized sluggish flycatcher of riverine and disturbed habitats. Key marks are entirely cinnamon plumage and large-headed, plain-faced appearance; bill seems heavy and is entirely black. Sits still, peering about, before sallying to foliage for insects. Inhabits mid-story and understory, often at forest edge. Found in forest along rivers and oxbow lakes, in abandoned plantations, and at savanna edges, usually near water. Similar to Dull-capped Attila but has dark eyes and different voice. Most common calls are various mournful whistles.
Tibetan Babax
Pterorhinus koslowi
A russet-brown babbler with pale eyes and a slightly curved black bill. Endemic to the eastern end of the Tibetan Plateau, where it inhabits areas with scrubby bushes and stunted trees. Generally, not as often seen around habitation as the larger, grayer Giant Babax (no range overlap), but will sometimes be seen taking handouts at monasteries. Forages on the ground, usually in pairs or small flocks.
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